Don't you see that they are different versions of the same thing?
I am in the same boat, I am also a long-time console collector. But Tighe (EDIT: Spoonmax), you need some rules to slim that down.
Let me see if I can help...
1. The easiest thing to get rid of will be the video game mags and strategy guides. A lot of the classic 1980 mags have been converted to PDFs. The strategy guides are the easiest to get rid of, all of that is online on Gamefaqs. Old paper starts to smell, you know. That frees up a lot of space.
2. Slim down the action figure collection. Keep Mai, but I think the Metal Gear guys can go.
3. If I only have 40 games for a particular system, I only have one.
4. If I have over 40 games, I buy a second console, just in case the first breaks. Get rid of anything extra. Really, you don't need three X-Boxes.
5. I would also get rid of the plushes. They will degrade, collect dust, and no child is going to want that. They have been produced in such quantity, they will be worthless in time. Give them to the local Ronald McDonald house or children's hospital.
6. Consider getting your money out of your Neo Geo AES stuff. A lot of that is available on compilations nowadays, which is only going to hurt the value of the originals, IMHO.
You have a very nice collection though, try these suggestions, but don't get rid of the bulk of it. It is something to be proud of!